Wildcard Certificate Validator

Validate wildcard certificate coverage and SAN entries

About Wildcard Certificates

A wildcard TLS certificate uses an asterisk (*) in the subject name (e.g., *.example.com) to secure unlimited subdomains on a single domain level. While convenient and cost-effective, wildcard certificates have specific coverage limitations and security considerations. Our Wildcard Certificate Validator examines a server's certificate to determine if it uses a wildcard, what domains it covers through SAN entries, and whether the coverage matches common deployment patterns.

How to Use

Enter the domain name (including subdomain if applicable) you want to check.
Optionally adjust the port number (default is 443).
Click Check to fetch and analyze the server's certificate.
Review the wildcard pattern, SAN entries, and coverage analysis in the results.

Use Cases

Certificate Planning: Determine if a wildcard or multi-SAN certificate better fits your infrastructure.
Deployment Verification: Confirm that your wildcard certificate covers all required subdomains after renewal.
Security Assessment: Review wildcard certificate usage and ensure it follows least-privilege principles.
Migration Support: Validate certificate coverage when migrating from wildcard to individual certificates.

Frequently Asked Questions

A wildcard certificate for *.example.com covers all single-level subdomains like www.example.com, mail.example.com, and api.example.com. However, it does NOT cover example.com (the bare domain) or multi-level subdomains like sub.www.example.com.

Wildcard certificates have security implications. If the private key is compromised, all subdomains are affected. Additionally, wildcard certificates cannot use domain validation methods that verify individual subdomains. Some organizations prefer individual certificates for better security isolation.

Yes, you can include the bare domain (example.com) as a separate SAN entry alongside the wildcard (*.example.com). Most CAs support this configuration, allowing the certificate to cover both the root domain and all single-level subdomains.

Tips & Best Practices

•Wildcard certificates only cover one level: *.example.com covers a.example.com but not a.b.example.com
•Ensure wildcard is installed on the correct server for intended subdomains
•Use SAN entries for specific subdomains alongside the wildcard
•Test wildcard certificates from multiple clients for consistent behavior

Technical Details

Patterns: *.domain.com wildcard format and coverage validation
Matching: Subdomain matching against wildcard patterns
SAN: Additional domain coverage verification
Chain: Complete certificate chain validation for wildcards